Recursive Loops - How to implement "Lucas Numbers" Algorithm?

Question

Hey,
I've seen other posts that are criticized to be more specific, so I hope I am clear in my questions.
I am trying to implement the Lucas Numbers series through a recursive loop. The formula is the following:
Ln = Ln-1 + Ln-2 for n>1
L0 = 2
L1 = 1
This is my first attempt at the code, which runs and gives horrible output for obvious reasons; my algorithm is probably incorrect.
//Based on the above algorithm, let Ln be L(int number)
public class RecursiveMethods{
    //int limit = 30;
    public RecursiveMethods(){
        //No Constructor Yet
    public int getLucasSequence(int number){ //Will print out
        if(number == 1){ //I don't know what to set the base case to.
            return number;
        else{
           // System.out.println(number);
            return number * getLucasSequence((number - 1) + number);  //Is this where the formula goes?  If so, how do I implement it?
public static void main(String [] args){
    //System.out.println("Test");
    RecursiveMethods myMethods = new RecursiveMethods();
    //System.out.println(myMethods.getLucasSequence(99));
    //for(int i = 0; i < 10; i++){ //Is this where you set the limit of iterations?
        System.out.println(myMethods.getLucasSequence(4)); //Value must not be one or two
}I have the following questions:
1) Based on the mathematical algorithm, how would I implement it in Java?
2) What would be the base case for a recursive loop that prints a series of Lucas Numbers
3) How would I set the limit on numbers?
I am a beginner programmer, so please explain these in terms I will be able to understand. I don't mind if you give hints too.
Thanks!
Chris

Answer 1

package recursives;
public class RecursiveMethods{
    public RecursiveMethods(){
        //No Constructor Yet
* @param number  specifies the index of the element in the Lucas sequence to be computed
    public int getLucasSequence(int number){ //Number should be Lnum
        if(number == 1){
            return number;
        else if(number == 0){ //The lucas sequence will always start off with 2...I forgot about this!
            return 2;
        else{
           // System.out.println(number);
            return getLucasSequence(number - 1) + getLucasSequence(number - 2); 
public static void main(String [] args){
    //System.out.println("Test");
    RecursiveMethods myMethods = new RecursiveMethods();
    //System.out.println(myMethods.getLucasSequence(99));
    //for(int i = 0; i < 10; i++){ //Is this where you set the limit of iterations?
        System.out.println(myMethods.getLucasSequence(3)); //Value must not be less than zero
}Sorry, I'm new to actually publishing code. Therefore, my coding style is very sloppy and usually uncommented. Thanks for the advice though, I will surely start implementing it in later projects!
Edited by: Chris.Y on Nov 3, 2008 4:38 AM